EP1739151B1 - Mesogenic compounds, liquid crystal medium and liquid display - Google Patents

Description

Field of the invention
• The present invention relates to mesogenic compounds, liquid crystal media comprising these compounds and to electro-optical displays comprising these mesogenic media as light modulation media, in particular to displays, which are operated at a temperature at which the mesogenic modulation media are in an optically isotropic phase, preferably in a blue phase.
Problem to be solved and state of the art
• Electro-optical displays and mesogenic light modulation media, which are in the isotropic phase when being operated in the display are described in DE 102 17 273 A . Electro-optical displays, and mesogenic light modulation media, which are in the optically isotropic blue phase, when being operated in the display are described in WO 2004/046 805 .
• The mesogenic media and displays described in these references provide several significant advantages compared to well-known and widely used displays using liquid crystals in the nematic phase, like for example liquid crystal displays (LCDs) operating in the twisted nematic (TN)-, the super twisted nematic (STN)-, the electrically controlled birefringence (ECB)-mode with its various modifications and the in-plane switching (IPS)-mode. Amongst these advantages are most pronounced their much faster switching times, and significantly wider optical viewing angle.
• Whereas, compared to displays using mesogenic media in another liquid crystalline phase, as e.g. in the smectic phase in surface stabilized ferroelectric liquid crystal displays (SSF LCDs), the displays of DE 102 17 273.0 and WO 2004/046 805 are much easier to manufacture. For example, they do not require a very thin cell gap and in addition the electro-optical effect is not very sensitive to small variations of the cell gap.
• XP 00083885, Nguyen, H.-T. et al., Advanced Materials 1997, 9, No. 5, pp 375-388, XP 000382046, Malthete, J. et al., Liq. Cryst.,1993, Vol. 13, No. 2, pp 171-187, XP 000483550, Zinsou, A. et al., Liq. Cryst., 1994, Vol. 17, No. 4, pp 513-28 and XP-001228661, Nishikawa, M. et al., Liq. Cryst., 2005, Vol. 32, No. 5, 585-598 do all teach mesogenic compounds having various substitution patterns, amongst which also compounds having three substituents on one or two terminal phenyl rings are mentioned.
• EP 0 721 933 A1 and DE 43 29 592 A1 are directed to mesogenic compounds having a 2,6-difluoro-1,4-phenylene moiety, which are shown to be useful for nematic liquid crystalline media.
• GB 2 216 523 A is_directed to mesogenic compounds having a 2,3-difluoro-1,4-phenylene moiety, which are also shown to be useful for nematic liquid crystalline media.
• XP 008048683, Nakata, M. et al., Phys. Rev. E, 2003, Vol. 68, pp 041710-1 -/6 is related to mesogenic media having a blue phase. It is teaching the introduction of blue phases by the use of certain non-chiral molecules to chiral nematic liquid crystals.
• However, the liquid crystal media described in these mentioned references still require operating voltages, which are not low enough for some applications. Further the operating voltages of these media vary with temperature, and it is generally observed, that at a certain temperature the voltage dramatically increases with increasing temperature. This limits the applicability of liquid crystal media in the blue phase for display applications. A further disadvantage of the liquid crystal media described in these patent applications is their moderate reliability which is insufficient for very demanding applications. This moderate reliability may be for example expressed in terms of the voltage holding ratio parameter (VHR), which in liquid crystal media as described above may be below 90%. Some compounds and compositions have been reported which possess a blue phase between the cholesteric phase and the isotropic phase and can usually be observed by optical microscopy. These compounds or compositions for which the blue phases are observed are typically single mesogenic compounds or mixtures showing a high chirality. However, generally the blue phases observed only extend over a very small temperature range, which is typically less than 1 degree centigrade wide, and/or the blue phase is located at rather inconvenient temperatures.
• In order to operate the novel fast switching display mode of WO 2004/046 805 the light modulation medium to be used has to be in the blue phase over a broad range of temperatures encompassing ambient temperature, however. Thus, a light modulation medium possessing a blue phase which is as wide as possible and conveniently located is required.
• Therefore there is a strong need for a modulation medium with a blue phase with a wide phase range, which may be achieved either by an appropriate mixture of mesogenic compounds themselves or, preferably by mixing a host mixture with appropriate mesogenic properties with a single dopant or a mixture of dopants that stabilises the blue phase over a wide temperature range.
• Summarizing, there is a need for liquid crystal media, which can be operated in liquid crystal displays, which are operated at temperatures where the media is in the blue phase, which provide the following technical improvements:
• a reduced operating voltage,
• a reduced temperature dependency of the operating voltage and
• an improved reliability, e.g. VHR.
Present invention
• Surprisingly, it now has been found that mesogenic media comprising one or more compounds of formula I shown below allow to enhance the width of the blue phase in respective media or lead to a decreased temperature dependence of the electro-optical response or an increase of the range of temperatures over which the temperature dependence is negligible or a to a combination of two or of all three of these effects.
• In a preferred embodiment of the present invention the compounds of formula I used according to the present invention are chiral compounds, preferably they comprise at least one chirally substituted atom and most preferably a chirally substituted C-atom.
• The compounds of the present invention and used according to the present invention are compounds of formula I

  

  wherein

R¹¹ to R¹⁶

are, independently of each other, alkyl, which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or poly-substituted by F, Cl, or CN, and in which one or more non-adjacent CH₂ groups are optionally replaced, in each case independently from one another, by -O-, -CH=CH- or -C≡C- in such a manner that O atoms are not linked directly to one another,

MG

is a bivalent mesogenic group and



or



or



and



MG

preferably is a bivalent mesogenic group of formula



wherein



is and, in case it is occurring more than once, also these are in each occurrence, independently of each other, an aromatic and/or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and/or S, and are optionally monosubstituted or polysubstituted by R,

R

has the meaning given for R¹¹ or is halogen, CN or



and preferably is halogen, CN, or alkyl, and most preferably F, CN or alkyl with 1 to 12 C-atoms,

Z¹¹ and Z¹²

are, independently of each other, and in case Z¹¹ is occurring more than once, also these are in each occurrence independently of each other, -O-, -S-, -CO-O-, -O-CO-, -O -CO-O-, -S-CO-, -CO-S-, -CO-NR⁰¹-, -NR⁰¹-CO-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CH₂CH₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰¹-, -CR⁰¹=CH-, -CY⁰¹=CY⁰²-, -C≡C-, -(CH₂)₄-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond, preferably -O-, -CO-O-, -O-CO-, -CF₂-O-, -O -CF₂ - or a single bond,

Y⁰¹ and Y⁰²

are, independently of each other, F, Cl or CN, and alternatively one of them may be H,

R⁰¹ and R⁰²

are, independently of each other, H or alkyl with 1 to 12 C-atoms,

m

is 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, and most preferably 1 or 2, and

n

is 0, 1 or 2, preferably 0 or 1, and most preferably 0.

• Chiral compounds are also encompassed by of formula I.
• Compounds of formula I are also an object of the present application.
• Preferred are compounds of formula I wherein the parameters have the following meaning

R¹¹ to R¹⁶

are, independently of each other, alkyl, alkoxy, alkenyl or alkynyl, preferably alkyl or alkoxy, most preferably alkoxy, and/or



preferably is, independently of each other in each occurrence,











or



and

wherein the rings optionally contain one or more hetero atoms selected from N, O and/or S, and are optionally monosubstituted or polysubstituted by R, which has the meaning given above, particularly preferred are


and

wherein

L¹¹ to L¹⁴

are, independently of each other, H or R, and/or

Z¹¹

is -O-, -CO-O-, -CF₂-O-, or a single bond, and/or

Z¹²

is -O-, -O -CO -, -O -CF₂ -, or a single bond.

• The compounds of formula I are preferably selected from the compounds it's sub-formulae I-i to I-v

  

  

  

  

  

  wherein the parameters have the respective meanings given above.
  In a preferred embodiment of the present invention rings A¹¹ are, independently of each other, an aromatic or alicyclic ring, preferably a 5-, 6- or 7-membered ring, or a group comprising two or more, preferably two or three, fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and/or S, and are optionally mono- or polysubstituted with L, wherein L is F, Cl, Br, CN, OH, NO₂, and/or an alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 12 C atoms, wherein one or more H atoms are optionally replaced by F or Cl.
• L is preferably F, Cl, CN, OH, NO₂, CH₃, C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂ or OC₂F₅, in particular F, Cl, CN, CH₃, C₂H₅, OCH₃, COCH₃ or OCF₃, most preferably F, Cl, CH₃, OCH₃ or COCH₃.
• Preferred rings A¹¹ are for example furane, pyrrol, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, cyclohexenylene, pyridine, pyrimidine, pyrazine, azulene, indane, naphthalene, tetrahydronaphthalene, decahydronaphthalene, tetrahydropyrane, anthracene, phenanthrene and fluorene.
• Particularly preferably one or more of these rings A¹¹ is, respectively are, selected from furane-2,5-diyl, thiophene-2,5-diyl, thienothiophene-2,5-diyl, dithienothiophene-2,6-diyl, pyrrol-2,5-diyl, 1,4-phenylene, azulene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, indane-2,5-diyl, or 1,4-cyclohexylene wherein one or two non-adjacent CH₂ groups are optionally replaced by ○ and/or S, wherein these groups are unsubstituted, mono- or polysubstituted by L as defined above.
• In a preferred embodiment of the present

  

  contains only monocyclic rings A¹¹. Very preferably this is a group containing one, two or three 5- and/or 6-membered rings.
• Preferred sub-formulae for these groups are listed below. For reasons of simplicity, Phe in these groups is 1,4-phenylene, PheL is a 1,4-phenylene group which is substituted by 1 to 4 groups L as defined above, Cyc is 1,4-cyclohexylene, Pyd is pyridine-2,5-diyl and Pyr is pyrimidine-2,5-diyl. The following list of preferred groups is comprising the sub formulae A-1 to A-20 as well as their mirror images,

  -Phe-	A-1
  -Pyd-	A-2
  -Pyr-	A-3
  -PheL-	A-4
  -Cyc-	A-5
  -Phe-Z-Cyc-	A-6
  -Cyc-Z-Cyc-	A-7
  -PheL-Cyc-	A-8
  -Phe-Z-Phe-	A-9
  -Phe-Z-Pyd-	A-10
  -Pyd-Z-Phe-	A-11
  -Phe-Z-Pyr-	A-12
  -Pyr-Z-Phe-	A-13
  -PheL-Z-Phe-	A-14
  -PheL-Z-Pyd-	A-15
  -PheL-Z-Pyr-	A-16
  -Pyr-Z-Pyd-	A-17
  -Pyd-Z-Pyd-	A-18
  -Pyr-Z-Pyr-	A-19
  -PheL-Z-PheL-	A-20

• In these preferred groups Z has the meaning of Z¹¹ as given in formula I. Preferably Z is -CF₂-O- or -O-CF₂- or a single bond.
• Very preferably, group

  

  is selected from the following formulae la to Ir and their respective mirror images

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  wherein L has the meaning given for L¹ above and r and s are independently of each other, 0, 1, 2, 3 or 4, preferably 0, 1 or 2.

  

  in these preferred formulae is very preferably

  

  furthermore

  

  with L having each independently one of the meanings given above.
• Especially preferred compounds of formula I comprise at least one group each in rings A¹¹ and A¹² of the formula

  

  wherein r is 1 to 2.
• Further preferred compounds of formula I comprise at least one group each in rings A¹¹, A¹² and A¹³ of the formula

  

  wherein r is 2 and/or at least one group each of the formula

  

  wherein r is 0, 1 or 2.
• Very preferably the group

  

  is selected from the following formulae and their respective mirror images

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  or

  

  wherein the 1,4-phenylene rings may optionally be substituted by R or L, preferably by alkyl, preferably by methyl, and/or by alkoxy and/or by halogen, preferably F.
• More preferably the group

  

  is selected from the following formulae and their respective mirror images

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  or

  
• An alkyl or an alkoxy radical, i.e. an alkyl where the terminal CH₂ group is replaced by -O-, in this application may be straight-chain or branched. It is preferably straight-chain, has 1, 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.
• Oxaalkyl, i.e. an alkyl group in which one non-terminal CH₂ group is replaced by -O-, is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-,7-, 8- or 9-oxadecyl, for example.
• An alkenyl group, i.e. an alkyl group wherein one or more CH₂ groups are replaced by -CH=CH-, may be straight-chain or branched. It is preferably straight-chain, has 2 to 10 C atoms and accordingly is preferably vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.
• Especially preferred alkenyl groups are C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, in particular C₂-C₇-1 E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl. Examples for particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 C atoms are generally preferred.
• In an alkyl group, wherein one CH₂ group is replaced by -O- and one by -CO-, these radicals are preferably neighboured. Accordingly these radicals together form a carbonyloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably such an alkyl group is straight-chain and has 2 to 6 C atoms.
• It is accordingly preferably acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.
• An alkyl group wherein two or more CH₂ groups are replaced by -O- and/or -COO-, it can be straight-chain or branched. It is preferably straight-chain and has 3 to 12 C atoms. Accordingly it is preferably bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl, 2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl, 4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl, 6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl, 8,8-bis-(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl, 2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl, 4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.
• A alkyl or alkenyl group that is monosubstituted by CN or CF₃ is preferably straight-chain. The substitution by CN or CF₃ can be in any desired position.
• An alkyl or alkenyl group that is at least monosubstituted by halogen, it is preferably straight-chain. Halogen is preferably F or Cl, in case of multiple substitution preferably F. The resulting groups include also perfluorinated groups. In case of monosubstitution the F or Cl substituent can be in any desired position, but is preferably in ω-position. Examples for especially preferred straight-chain groups with a terminal F substituent are fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. Other positions of F are, however, not excluded.
• Halogen means F, Cl, Br and I and is preferably F or Cl, most preferably F. Each of R¹¹, R¹², R¹³, R, R' and R" may be a polar or a non-polar group. In case of a polar group, it is preferably selected from CN, SF₅, halogen, OCH₃, SCN, COR⁵, COOR⁵ or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R⁵ is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferred polar groups are selected of F, Cl, CN, OCH₃, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, CHF₂, CH₂F, OCF₃, OCHF₂, OCH₂F, C₂F₅ and OC₂F₅, in particular F, Cl, CN, CF₃, OCHF₂ and OCF₃. In case of a non-polar group, it is preferably alkyl with up to 15 C atoms or alkoxy with 2 to 15 C atoms.
• Each of R¹¹, R¹², R¹³ R, and R' may be an achiral or a chiral group. In case of a chiral group it is preferably of formula I*:

  

  wherein

Q¹

is an alkylene or alkylene-oxy group with 1 to 9 C atoms or a single bond,

Q²

is an alkyl or alkoxy group with 1 to 10 C atoms which may be unsubstituted, mono- or polysubstituted by F, Cl, Br or CN, it being also possible for one or more non-adjacent CH₂ groups to be replaced, in each case independently from one another, by -C≡C-, -O-, -S-, -NH-, -N(CH₃)-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO- or -CO-S- in such a manner that oxygen atoms are not linked directly to one another,

Q³

is F, Cl, Br, CN or an alkyl or alkoxy group as defined for Q² but being different from Q².

• In case Q¹ in formula I* is an alkylene-oxy group, the O atom is preferably adjacent to the chiral C atom.
• Preferred chiral groups of formula I* are 2-alkyl, 2-alkoxy, 2-methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy, 2-(2-ethin)-alkyl, 2-(2-ethin)-alkoxy, 1,1,1-trifluoro-2-alkyl and 1,1,1-trifluoro-2-alkoxy.
• Particularly preferred chiral groups I* are 2-butyl (=1-methylpropyl), 2-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-methylbutyryloxy, 3-methylvaleroyloxy, 4-methylhexanoyloxy, 2-chlorpropionyloxy, 2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy, 2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy, 1,1,1-trifluoro-2-octyl, 2-fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-trifluoro-2-octyl and 1,1,1-trifluoro-2-octyloxy.
• In addition, compounds containing an achiral branched alkyl group may occasionally be of importance, for example, due to a reduction in the tendency towards crystallization. Branched groups of this type generally do not contain more than one chain branch. Preferred achiral branched groups are isopropyl, isobutyl (= methylpropyl), isopentyl (= 3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3-methylbutoxy.
• In a preferred embodiment of the present invention one or more of R¹¹, R¹², R¹³, R, and R' are -SG-PG.
• Particularly preferred are compounds of formula I and its sub-formulae wherein R¹¹ is -SG-PG and additionally preferred m is 0 at the same time.
• The polymerisable or reactive group PG is preferably selected from CH₂=CW¹-COO-,

  

  CH₂=CW²-(O)_k1-, CH₃-CH=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, HO-CW²W³-, HS-CW²W³-, HW²N-, HO-CW²W³-NH-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)_k1-Phe-(O)_k2-, Phe-CH=CH-, HOOC-, OCN-, and W⁴W⁵W⁶Si-, with W¹ being H, Cl, CN, phenyl or alkyl with 1 to 5 C-atoms, in particular H, Cl or CH₃, W² and W³ being independently of each other H or alkyl with 1 to 5 C-atoms, in particular methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ being independently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phe being 1,4-phenylene and k₁ and k₂ being independently of each other 0 or 1.
• Especially preferably PG is a vinyl group, an acrylate group, a methacrylate group, an oxetane group or an epoxy group, especially preferably an acrylate or methacrylate group.
• As for the spacer group SG all groups can be used that are known for this purpose to those skilled in the art. The spacer group SG is preferably of formula SG'-X, such that PG-SG- is PG-SG'-X-, wherein

SG'

is alkylene with up to 20 C atoms which may be unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, it being also possible for one or more non-adjacent CH₂ groups to be replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR⁰¹-, -SiR⁰¹R⁰²-, -CO-, -COO-, -OCO-, -OCO-O-, -S-, -CO-, -CO-S-, -CH=CH- or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another,

X

is -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR⁰¹-, -NR⁰¹-CO-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰¹-, -CY⁰¹=CY⁰²-, -C≡C-, -CH=CH-COO-, -OCO-, -CH=CH- or a single bond,and

R⁰¹,R⁰², Y⁰¹ and Y⁰²

have one of the respective meanings given above.

X

is preferably -O-, -S-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CH₂CH₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰-, -CY⁰²=CY⁰²-, -C≡C- or a single bond, in particular -O-, -S-, -C≡C-, -CY⁰¹=CY⁰²- or a single bond, very preferably a group that is able to from a conjugated system, such as -C≡C- or -CY⁰¹=CY⁰²-, or a single bond.

• Typical groups SG' are, for example, -(CH₂)_p-, -(CH₂CH₂O)_q-CH₂CH₂-, -CH₂CH₂-S-CH₂CH₂- or -CH₂CH₂-NH-CH₂CH₂- or -(SiR⁰R⁰⁰-O)_p-, with p being an integer from 2 to 12, q being an integer from 1 to 3 and R⁰, R⁰⁰ and the other parameters having the meanings given above.
• Preferred groups SG' are ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylene-thioethylene, ethylene-N-methyl-iminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene for example.
• In another preferred embodiment SG' is a chiral group of formula 1*':

  

  wherein

Q¹ and Q³

have the meanings given in formula I*, and

Q⁴

is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, being different from Q¹,

with Q¹ being linked to the polymerisable group PG.
• Further preferred are compounds with one or two groups PG-SG- wherein SG is a single bond.
• In case of compounds with two groups PG-SG, each of the two polymerisable groups PG and the two spacer groups SG can be identical or different.
• Preferable compounds according to the instant invention are the following exemplary compounds

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  
• Preferably the liquid crystalline media according to the instant invention contain a component A comprising, preferably predominantly consisting of and most preferably entirely consisting of compounds of formula I.
• The compounds of formula I are accessible by the usual methods known to the expert.
• Compounds of formula I are beneficially prepared e.g. according to one of the following two exemplary reaction schemes (schemes I and II) and analogous synthetic routes.

  

  wherein preferably R is alkyl and the phenyl rings each may optionally be substituted by one or more F-atoms.

  

  wherein preferably R is alkyl and the phenyl rings each may optionally be substituted by one or more F-atoms.
• Comprising in this application means in the context of compositions that the entity referred to, e.g. the medium or the component, contains the compound or compounds in question, preferably in a total concentration of 10 % or more and most preferably of 20 % or more.
• Predominantly consisting, in this context, means that the entity referred to contains 80 % or more, preferably 90 % or more and most preferably 95 % or more of the compound or compounds in question.
• Entirely consisting, in this context, means that the entity referred to contains 98 % or more, preferably 99 % or more and most preferably 100.0 % of the compound or compounds in question.
  The concentration of the compounds according to the present application are contained in the media according to the present application preferably is in the range from 0.5% or more to 30% or less, more preferably in the range from 1 % or more to 20% or less and most preferably in the range from 5% or more to 12% or less.
• In a preferred embodiment the mesogenic modulation media according to the instant invention comprise
• a component A, preferably in a concentration of 1 % to 25 % by weight, comprising, preferably predominantly consisting of and most preferably entirely consisting of, one compound or more compounds of the formula I given above and
• optionally a dielectrically positive component B comprising, preferably predominantly consisting of and most preferably entirely consisting of one compound or of more compounds of formula II
  
  wherein

  R²

  has the meaning given under formula I for R¹¹,

  A²¹, A²² and A²³

  are, each independently of each other,

  

  whereby each of A²¹ and A²² may have the same or a different meaning if present twice,

  Z²¹ and Z²²

  are, each independently of each other, a single bond, -(CH₂)₄)-, -CH₂CH₂-, -CF₂-CF₂-, -CF₂-CH₂-, -CH₂-CF₂-, -CH=CH-, -CF=CF-, -CF=CH-, -(CH₂)₃O-, -O(CH₂)₃-, -CH=CF-, -C≡C-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂-, -CO-O- or -O-CO-, whereby each of Z²¹ and Z²² may have the same or a different meaning if present twice,

  X²

  is halogen, -CN, -NCS, -SF₅, -SO₂CF₃, alkyl, alkenyl, alkenyloxy or alkylalkoxy or alkoxy radical each mono- or polysubstituted by CN and/or halogen,

  L²¹ and L²²

  are, each independently of each other, H or F, and

  m

  is 0, 1 or 2,

  n

  is 0, 1, 2 or 3,

  o

  is 0, 1 or 2, preferably 0 or 1 and

  m + n + o

  is 3 or less, preferably 2 or less,

• optionally a component C, preferably in a concentration of 1 % to 25 % by weight, comprising, preferably predominantly consisting of and most preferably entirely consisting of one compound or of more compounds of formula III
  
  wherein

  a, b, c and d

  are each independently of each other 0, 1 or 2, whereby

  a+b+c+d

  is 4 or less,

  A³¹, A³², A³³ and A³⁴

  are, each independently of each other,

  

  whereby each of A³¹, A³², A³³ and A³⁴ may have the same or a different meaning if present twice,

  Z³¹, Z³², Z³³ and Z³⁴

  are, each independently of each other, a single bond, -(CH₂)₄)-, -CH₂CH₂-, -CF₂-CF₂-, -CF₂-CH₂-, -CH₂-CF₂-, -CH=CH-, -CF=CF-, -CF=CH-, -(CH₂)₃O-, -O(CH₂)₃-, -CH=CF-, -C≡D-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂-, -CO-O- or -O-CO-, whereby each of Z³¹, Z³², Z³³ and Z³⁴ may have the same or a different meaning if present twice,

  R³

  is an alkyl or alkoxy radical having from 1 to 15 carbon atoms, wherein one or more methylene groups of said alkyl or alkoxy radical may be replaced independently of each other by -O-, -S-, -SiR^xR^y-, -CH=CH-, -C≡D-, -CO-O- and/or -O-CO- such that oxygen and/or sulfur atoms are not linked directly to each other, said alkyl or alkoxy radical being unsubstituted or mono-substituted with a -CN group or mono- or poly-substituted with halogen, preferably R¹¹ is a straight-chain alkyl, alkoxy, alkenyl, alkenyloxy or -O-alkylene-O-alkyl radical with up to 10 carbon atoms, said radicals being unsubstituted or mono- or poly-substituted with halogen,

  L³¹, L³², L³³ and L³⁴

  are each independently of each other hydrogen, halogen, a CN group, an alkyl or alkoxy radical having from 1 to 15 carbon atoms wherein one or more methylene groups of said alkyl or alkoxy radical may be replaced independently of each other by -O-, -S-, -SiR^xR^y-, -CH=CH-, -C≡D-, -CO-O- and/or -O-CO- such that oxygen and/or sulfur atoms are not linked directly to each other, said alkyl or alkoxy radical being unsubstituted or mono-substituted with a -CN group or mono- or poly-substituted with halogen, with the proviso that at least one of L³¹, L³², L³³ and L³⁴ is not hydrogen,

  X³

  is F, Cl, CF₃, OCF₃, CN, NCS, -SF₅ or -SO₂-R^z,

  R^x and R^y

  are independently of each other hydrogen or an alkyl radical having from 1 to 7 carbon atoms; preferably R^x and R^y are both methyl, ethyl, propyl or butyl, and

  R^z

  is an alkyl radical having from 1 to 7 carbon atoms, said alkyl radical being unsubstituted or mono- or poly-substituted with halogen; preferably R^z is CF₃, C₂F₅ or n-C₄Fg and

• 1-20 % by weight of component D comprising one chiral compound or more chiral compounds with a HTP of ≥20 µm.
• The inventive mixtures contain 1-25 wt.%, preferably 2-20 wt.% and most preferably 3-15 wt.% of component A.
• Suitable chiral compounds of component D are those which have an absolute value of the helical twisting power of 20 µm or more, preferably of 40 µm or more and most preferably of 60 µm or more. The HTP is measured in MLC-6260 at a temperature of 20°C.
• The chiral component D comprises preferably one or more chiral compounds which have a mesogenic structure und exhibit preferably one or more mesophases themselves, particularly at least one cholesteric phase. Preferred chiral compounds being comprised in the chiral component D are, amongst others, well known chiral dopants like cholesteryl- nonanoate (CN), R/S-811, R/S-1011, R/S-2011, R/S-3011, R/S-4011, R/S-5011, CB-15 (Merck KGaA, Darmstadt, Germany). Preferred are chiral dopants having one or more chiral moieties and one or more mesogenic groups or having one or more aromatic or alicyclic moieties forming, together with the chiral moiety, a mesogenic group. More preferred are chiral moieties and mesogenic chiral compounds disclosed in DE 34 25 503 , DE 35 34 777 , DE 35 34 778 , DE 35 34 779 , DE 35 34 780 , DE 43 42 280 , EP 01 038 941 and DE 195 41 820 that disclosure is incorporated within this application by way of reference. Particular preference is given to chiral binaphthyl derivatives as disclosed in EP 01 111 954.2 , chiral binaphthol derivatives as disclosed in WO 02/34739 , chiral TADDOL derivatives as disclosed in WO 02/06265 as well as chiral dopants having at least one fluorinated linker and one end chiral moiety or one central chiral moiety as disclosed in WO 02/06196 and WO 02/06195 .
• The controlling medium of the present invention has a characteristic temperature, preferably a clearing point, in the range from about -30 °C to about 80 °C, especially up to about 55 °C.
• The inventive mixtures contain one ore more (two, three, four or more) chiral compounds in the range of 1-25 wt.%, preferably 2-20 wt.%. Especially preferred are mixtures containing 3-15 wt.% of a chiral compound.
• Preferred embodiments are indicated below:
• The medium comprises one, two or more compounds of formula I;
• Component B preferably contains besides one compound ore more compounds of formula II one ester compound or more ester compounds of the formula Z
  
  wherein R^Z has the meaning given under formula I for R¹¹,
  

  X^Z

  is F, Cl, CN, NCS, OCF₃, CF₃ or SF₅.

  wherein R^Z has the meaning given under formula II for R².
  Especially preferred are mixtures containing 5 % to 35 %, preferably 10 % to 30 % and especially preferred 10 % to 20 % of compounds of formula Z.
• The component B preferably contains additionally one or more compounds of formula N
  
wherein

R

has the meaning given under formula I for R¹¹ and preferably is alkyl or Alkyl-C≡C,

"Alkyl"

is alkyl with 1 to 7 C-atoms, preferably n-alkyl, and

n

is 0 or 1.

• The component B preferably additionally comprises one or more compounds selected from the group of ester compounds of formula E
  
  in which R⁰ has the meaning given for R¹¹ under formula I and preferably is alkyl and
  
  is
• The proportion of the compounds of formula E is preferably 10-30% by weight, in particular 15 % to 25 %.
• The medium preferably comprises one compound or more compounds selected from the group of formulae Q-1 and Q-2
  
  
  wherein R⁰ has the meaning given for R¹¹ under formula I and n and m are, independently of each other 0 or 1.
• The medium preferably comprises one compound or more compounds selected from the group of compounds of formula II in which R⁰ is methyl.
• The medium preferably comprises one dioxane compound, two or more dioxane compounds, preferably one dioxane compound or two dioxane compounds, selected from the group of formulae Dx-1 and Dx-2
  
  
wherein R⁰ has the meaning given for R¹¹ under formula I.
• It has been found that even a relatively small proportion of compounds of the formula I mixed with conventional liquid-crystal materials, but in particular with one or more compounds of the formulae II and III, results in a lower operating voltage and a broader operating temperature range. Preference is given, in particular, to mixtures which, besides one or more compounds of the formula I, comprise one or more compounds of the formula II, in particular compounds of the formula II in which X² is F, Cl, CN, NCS, CF₃ or OCF₃. The compounds of the formulae I to III are colourless, stable and readily miscible with one another and with other liquid-crystalline materials.
• The optimum mixing ratio of the compounds of the formulae I and II and III depends substantially on the desired properties, on the choice of the components of the formulae I, II and/or III, and on the choice of any other components that may be present. Suitable mixing ratios within the range given above can easily be determined from case to case.
• The total amount of compounds of the formulae I to III in the mixtures according to the invention is not crucial. The mixtures can therefore comprise one or more further components for the purposes of optimisation of various properties. However, the observed effect on the operating voltage and the operating temperature range is generally greater, the higher the total concentration of compounds of the formulae I to III.
• In a particularly preferred embodiment, the media according to the invention comprise compounds of the formula III which X³ is F, OCF₃, OCHF₂, OCH=CF₂, OCF=CF₂ or OCF₂-CF₂H. A favourable synergistic effect with the compounds of the formula I results in particularly advantageous properties. In particular, mixtures comprising compounds of formula I and of formula II and of formula III are distinguished by their low operating voltages.
• The individual compounds of the formulae II to III which can be used in the media according to the invention are either known or can be prepared analogously to the known compounds.
• The construction of the MLC display according to the invention from polarisers, electrode base plates and surface-treated electrodes corresponds to the conventional construction for displays of this type. The term conventional construction is broadly drawn here and also covers all derivatives and modifications of the MLC display, in particular including matrix display elements based on poly-Si TFT or MIM, however, particularly preferred are displays, which have electrodes on just one of the substrates, i.e. so called interdigital electrodes, as those used in IPS displays, preferably in one of the established structures.
• A significant difference between the displays according to the invention and the conventional displays based on the twisted nematic cell consists, however, in the choice of the liquid-crystal parameters of the liquid-crystal layer.
• The media according to the invention are prepared in a manner conventional per se. In general, the components are dissolved in one another, advantageously at elevated temperature. By means of suitable additives, the liquid-crystalline phases in accordance with the invention can be modified in such a way that they can be used in all types of liquid crystal display elements that have been disclosed hitherto. Additives of this type are known to the person skilled in the art and are described in detail in the literature (H. Kelker and R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be added for the preparation of coloured guest-host systems or substances can be added in order to modify the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Furthermore, stabilisers and antioxidants can be added.
• The mixtures according to the invention are suitable for TN, STN, ECB and IPS applications and isotropic switching mode (ISM) applications. Hence, there use in an electro-optical device and an electro-optical device containing liquid crystal media comprising at least one compound according to the invention are subject matters of the present invention.
• The inventive mixtures are highly suitable for devices which operate in an optically isotropic state. The mixtures of the invention are surprisingly found to be highly suitable for the respective use.
• Electro-optical devices that are operated or operable in an optically isotropic state recently have become of interest with respect to video, TV, and multi-media applications. This is because conventional liquid crystal displays utilizing electro-optical effects based on the physical properties of liquid crystals exhibit a rather high switching time which is undesired for said applications. Furthermore most of the conventional displays show a significant viewing angle dependence of contrast that in turn makes necessary measures to compensate this undesired property.
• With regard to devices utilizing electro-optical effects in an isotropic state the German Patent Application DE 102 17 273 A1 for example discloses light controlling (light modulation) elements in which the mesogenic controlling medium for modulation is in the isotropic phase at the operating temperature. These light controlling elements have a very short switching time and a good viewing angle dependence of contrast. However, the driving or operating voltages of said elements are very often unsuitably high for some applications.
• German Patent Application DE 102 41 301 yet unpublished describes specific structures of electrodes allowing a significant reduction of the driving voltages. However, these electrodes make the process of manufacturing the light controlling elements more complicated.
• Furthermore, the light controlling elements, for example, disclosed in both DE 102 17 273 A1 and DE 102 41 301 show a significant temperature dependence. The electro-optical effect that can be induced by the electrical field in the controlling medium being in an optical isotropic state is most pronounced at temperatures close to the clearing point of the controlling medium. In this range the light controlling elements have the lowest values of their characteristic voltages and, thus, require the lowest operating voltages. As temperature increases the characteristic voltages and hence the operating voltages increase remarkably. Typical values of the temperature dependence are in the range from about a few volts per centigrade up to about ten or more volts per centigrade. While DE 102 41 301 describes various structures of electrodes for devices operable or operated in the isotropic state, DE 102 17 273 A1 discloses isotropic media of varying composition that are useful in light controlling elements operable or operated in the isotropic state. The relative temperature dependence of the threshold voltage in these light controlling elements is at a temperature of 1 centigrade above the clearing point in the range of about 50%/centigrade. That temperature dependence decreases with increasing temperature so that it is at a temperature of 5 centigrade above the clearing point of about 10%/centigrade. However, for many practical applications of displays utilizing said light controlling elements the temperature dependence of the electro-optical effect is too high. To the contrary, for practical uses it is desired that the operating voltages are independent from the operating temperature over a temperature range of at least some centigrades, preferably of about 5 centigrades or more, even more preferably of about 10 centigrades or more and especially of about 20 centigrades or more.
• Now it has been found that the use of the inventive mixtures are highly suitable as controlling media in the light controlling elements as described above and in DE 102 17 273 A1 , DE 102 41 301 and DE 102 536 06 and broaden the temperature range in which the operating voltages of said electro-optical operates. In this case the optical isotropic state or the blue phase is almost completely or completely independent from the operating temperature.
• This effect is even more distinct if the mesogenic controlling media exhibit at least one so-called "blue phase" as described in yet unpublished WO 2004/046 805 . Liquid crystals having an extremely high chiral twist may have one or more optically isotropic phases. If they have a respective cholesteric pitch, these phases might appear bluish in a cell having a sufficiently large cell gap. Those phases are therefore also called "blue phases" (Gray and Goodby, "Smectic Liquid Crystals, Textures and Structures", Leonhard Hill, USA, Canada (1984)). Effects of electrical fields on liquid crystals existing in a blue phase are described for instance in H.S. Kitzerow, "The Effect of Electric Fields on Blue Phases", Mol. Cryst. Liq. Cryst. (1991), Vol. 202, p. 51-83, as well as the three types of blue phases identified so far, namely BP I, BP II, and BP III, that may be observed in field-free liquid crystals. It is noteworthy, that if the liquid crystal exhibiting a blue phase or blue phases is subjected to an electrical field, further blue phases or other phases different from the blue phases I, II and III might appear.
• The inventive mixtures can be used in an electro-optical light controlling element, which comprises
• one or more, especially two substrates;
• an assembly of electrodes;
• one or more elements for polarizing the light; and
• said controlling medium;
whereby said light controlling element is operated (or operable) at a temperature at which the controlling medium is in an optically isotropic phase when it is in a non-driven state.
• The controlling medium of the present invention has a characteristic temperature, preferably a clearing point, in the range from about -30 °C to about 80 °C, especially up to about 55 °C.
• The operating temperature of the light controlling elements is preferably above the characteristic temperature of the controlling medium said temperature being usually the transition temperature of the controlling medium to the blue phase; generally the operating temperature is in the range of about 0.1 ° to about 50 °, preferably in the range of about 0.1 ° to about 10 ° above said characteristic temperature. It is highly preferred that the operating temperature is in the range from the transition temperature of the controlling medium to the blue phase up to the transition temperature of the controlling medium to the isotropic phase which is the clearing point. The light controlling elements, however, may also be operated at temperatures at which the controlling medium is in the isotropic phase. (For the purposes of the present invention the term "characteristic temperature" is defined as follows:
• If the characteristic voltage as a function of temperature has a minimum, the temperature at this minimum is denoted as characteristic temperature.
• If the characteristic voltage as a function of temperature has no minimum and if the controlling medium has one or more blue phases, the transition temperature to the blue phase is denoted as characteristic temperature; in case there are more than one blue phase, the lowest transition temperature to a blue phase is denoted as characteristic temperature.
• If the characteristic voltage as a function of temperature has no minimum and if the controlling medium has no blue phase, the transition temperature to the isotropic phase is denoted as characteristic temperature.)
• In the context of the present invention the term "alkyl" means, as long as it is not defined in a different manner elsewhere in this description or in the claims, straight-chain and branched hydrocarbon (aliphatic) radicals with 1 to 15 carbon atoms. The hydrocarbon radicals may be unsubstituted or substituted with one or more substituents being independently selected from the group consisting of F, Cl, Br, I or CN.
• The dielectrics may also comprise further additives known to the person skilled in the art and described in the literature. For example, 0 to 5% of pleochroic dyes, antioxidants or stabilizers can be added.
• C denotes a crystalline phase, S a smectic phase, S_C a smectic C phase, N a nematic phase, I the isotropic phase and BP the blue phase.
• V_X denotes the voltage for X% transmission. Thus e.g. V₁₀ denotes the voltage for 10% transmission and V₁₀₀ denotes the voltage for 100% transmission (viewing angle perpendicular to the plate surface). t_on (respectively τ_on) denotes the switch-on time and t_off (respectively τ_off) the switch-off time at an operating voltage corresponding the value of V₁₀₀, respectively of V_max.
• Δn denotes the optical anisotropy. Δε denotes the dielectric anisotropy (Δε = ε_∥ - ε_⊥, where ε_∥ denotes the dielectric constant parallel to the longitudinal molecular axes andε_∥ denotes the dielectric constant perpendicular thereto). The electro-optical data are measured in a TN cell at the 1^st minimum of transmission (i.e. at a (d · Δn) value of 0.5 µm) at 20°C, unless expressly stated otherwise. The optical data are measured at 20°C, unless expressly stated otherwise.
• Optionally, the light modulation media according to the present invention can comprise further liquid crystal compounds in order to adjust the physical properties. Such compounds are known to the expert. Their concentration in the media according to the instant invention is preferably 0 % to 30 %, more preferably 0 % to 20 % and most preferably 5 % to 15 %.
• Preferably inventive media have a range of the blue phase or, in case of the occurrence of more than one blue phase, a combined range of the blue phases, with a width of 9° or more, preferably of 10° or more, more preferably of 15° or more and most preferably of 20° or more.
• In a preferred embodiment this phase range at least from 10°C to 30°C, most preferably at least from 10°C to 40°C and most preferably at least from 0°C to 50°C, wherein at least means, that preferably the phase extends to temperatures below the lower limit and at the same time, that it extends to temperatures above the upper limit.
• In another preferred embodiment this phase range at least from 20°C to 40°C, most preferably at least from 30°C to 80°C and most preferably at least from 30°C to 90°C. This embodiment is particularly suited for displays with a strong back light, dissipating energy and thus heating the display.
• In the present application the term dielectrically positive compounds describes compounds with Δε > 1,5, dielectrically neutral compounds are compounds with -1,5 ≤ Δε ≤ 1,5 and dielectrically negative compounds are compounds with Δε < -1,5. The same holds for components. Δε is determined at 1 kHz and 20 °C. The dielectrical anisotropies of the compounds is determined from the results of a solution of 10 % of the individual compounds in a nematic host mixture. The capacities of these test mixtures are determined both in a cell with homeotropic and with homogeneous alignment. The cell gap of both types of cells is approximately 20 µm. The voltage applied is a rectangular wave with a frequency of 1 kHz and a root mean square value typically of 0.5 V to 1.0 V, however, it is always selected to be below the capacitive threshold of the respective test mixture.
• For dielectrically positive compounds the mixture ZLI-4792 and for dielectrically neutral, as well as for dielectrically negative compounds, the mixture ZLI-3086, both of Merck KGaA, Germany are used as host mixture, respectively. The dielectric permittivities of the compounds are determined from the change of the respective values of the host mixture upon addition of the compounds of interest and are extrapolated to a concentration of the compounds of interest of 100 %.
• Components having a nematic phase at the measurement temperature of 20 °C are measured as such, all others are treated like compounds.
• The term threshold voltage refers in the instant application to the optical threshold and is given for 10 % relative contrast (V₁₀) and the term saturation voltage refers to the optical saturation and is given for 90 % relative contrast (V₉₀) both, if not explicitly stated otherwise. The capacitive threshold voltage (V₀, also called Freedericksz-threshold V_Fr) is only used if explicitly mentioned.
• The ranges of parameters given in this application are all including the limiting values, unless explicitly stated otherwise.
• Throughout this application, unless explicitly stated otherwise, all concentrations are given in mass percent and relate to the respective complete mixture, all temperatures are given in degrees centigrade (Celsius) and all differences of temperatures in degrees centigrade. All physical properties have been and are determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany and are given for a temperature of 20 °C, unless explicitly stated otherwise. The optical anisotropy (Δn) is determined at a wavelength of 589.3 nm. The dielectric anisotropy (Δε) is determined at a frequency of 1 kHz. The threshold voltages, as well as all other electro-optical properties have been determined with test cells prepared at Merck KGaA, Germany. The test cells for the determination of Δε had a cell gap of 22 µm. The electrode was a circular ITO electrode with an area of 1.13 cm² and a guard ring. The orientation layers were lecithin for homeotropic orientation (ε||) and polyimide AL-1 054 from Japan Synthetic Rubber for homogenous orientation (ε_⊥). The capacities were determined with a frequency response analyser Solatron 1260 using a sine wave with a voltage of 0.3 or 0.1 V_rms. The light used in the electro-optical measurements was white light. The set up used was a commercially available equipment of Otsuka, Japan. The characteristic voltages have been determined under perpendicular observation. The threshold voltage (V₁₀), mid-grey voltage (V₅₀) and saturation voltage (V₉₀) have been determined for 10 %, 50 % and 90 % relative contrast, respectively.
• The mesogenic modulation material has been filled into an electro optical test cell prepared at the respective facility of Merck KGaA. The test cells had inter-digital electrodes on one substrate side. The electrode width was 10 µm, the distance between adjacent electrodes was 10 µm and the cell gap was also 10 µm. This test cell has been evaluated electro-optically between crossed polarisers.
• At low temperatures, the filled cells showed the typical texture of a chiral nematic mixture, with an optical transmission between crossed polarisers without applied voltage. Upon heating, at a first temperature (T₁) the mixtures turned optically isotropic, being dark between the crossed polarisers. This indicated the transition from the chiral nematic phase to the blue phase at that temperature. Up to a second temperature (T₂) the cell showed an electro-optical effect under applied voltage, typically of some tens of volts, a certain voltage in that range leading to a maximum of the optical transmission. Typically at a higher temperature the voltage needed for a visible electro-optical effect increased strongly, indicating the transition from the blue phase to the isotropic phase at this second temperature (T₂).
• The temperature range (ΔT(BP)), where the mixture can be used electro-optically in the blue phase most beneficially has been identified as ranging from T₁ to T₂. This temperature range (ΔT(BP)) is the temperature range given in the examples of this application. The electro-optical displays can also be operated at temperatures beyond this range, i.e. at temperatures above T₂, albeit only at significantly increased operation voltages.
• The liquid crystal media according to the present invention can contain further additives and chiral dopants in usual concentrations. The total concentration of these further constituents is in the range of 0 % to 10 %, preferably 0.1 % to 6 %, based in the total mixture. The concentrations of the individual compounds used each are preferably in the range of 0.1 to 3 %. The concentration of these and of similar additives is not taken into consideration for the values and ranges of the concentrations of the liquid crystal components and compounds of the liquid crystal media in this application.
• The inventive liquid crystal media according to the present invention consist of several compounds, preferably of 3 to 30, more preferably of 5 to 20 and most preferably of 6 to 14 compounds. These compounds are mixed in conventional way. As a rule, the required amount of the compound used in the smaller amount is dissolved in the compound used in the greater amount. In case the temperature is above the clearing point of the compound used in the higher concentration, it is particularly easy to observe completion of the process of dissolution. It is, however, also possible to prepare the media by other conventional ways, e. g. using so called pre-mixtures, which can be e. g. homologous or eutectic mixtures of compounds or using so called multi-bottle-systems, the constituents of which are ready to use mixtures themselves.
• By addition of suitable additives, the liquid crystal media according to the instant invention can be modified in such a way, that they are usable in all known types of liquid crystal displays, either using the liquid crystal media as such, like TN-, TN-AMD, ECB-, VAN-AMD and in particular in composite systems, like PDLD-, NCAP- and PN-LCDs and especially in HPDLCs.
• The melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T (N,I) of the liquid crystals are given in degrees centigrade.
• In the present application and especially in the following examples, the structures of the liquid crystal compounds are represented by abbreviations also called acronyms. The transformation of the abbreviations into the corresponding structures is straight forward according to the following two tables A and B. All groups C_nH_2n+1 and C_mH_2m+1 are straight chain alkyl groups with n respectively m C-atoms. The interpretation of table B is self evident. Table A does only list the abbreviations for the cores of the structures. The individual compounds are denoted by the abbreviation of the core followed by a hyphen and a code specifying the substituents R¹, R², L¹ and L² follows:

  Code for R1, R2, L1, L2	R1	R2	L1	L2
  nm	CnH2n+1	CmH2m+1	H	H
  nOm	CnH2n+1	OCmH2m+1	H	H
  nO.m	OCnH2n+1	CmH2m+1	H	H
  n	CnH2n+1	CN	H	H
  nN.F	CnH2n+1	CN	H	F
  nN.F.F	CnH2n+1	CN	F	F
  nF	CnH2n+1	F	H	H
  nF.F	CnH2n+1	F	H	F
  nF.F.F	CnH2n+1	F	F	F
  nOF	OCnH2n+1	F	H	H
  nCl	CnH2n+1	Cl	H	H
  nCl.F	CnH2n+1	Cl	H	F
  nCl.F.F	CnH2n+1	Cl	F	F
  nCF3	CnH2n+1	CF3	H	H
  nOCF3	CnH2n+1	OCF3	H	H
  nOCF3.F	CnH2n+1	OCF3	H	F
  nOCF3.F.F	CnH2n+1	OCF3	F	F
  nOCF2	CnH2n+1	OCHF2	H	H
  nOCF2.F	CnH2n+1	OCHF2	H	F
  nOCF2.F.F	CnH2n+1	OCHF2	F	F
  nS	CnH2n+1	NCS	H	H
  nS.F	CnH2n+1	NCS	H	F
  nS.F.F	CnH2n+1	NCS	F	F
  rVsN	CrH2r+1-CH=CH-CsH2s-	CN	H	H
  rEsN	CrH2r+1-O-CsH2s-	CN	H	H
  nAm	CnH2n+1	COOCmH2m+1	H	H
  nF.Cl	CnH2n+1	Cl	H	F

  Table A:

  PCH	EPCH
  BCH	CCP
  CECP	ECCP
  BECH	EBCH
  PTP	CPTP
  CEPTP
  CCH	PDX
  PYP	PYRP
  D	ME
  HP	CP
  EHP
  ET
  FET

  Table B:

  CGP-n-X (X = F, CF3, OCHF2 or OCF3)	CGG-N-X (X = F, CF3, OCHF2 or OCF3)
  CGU-n-X (X = F, CF3, OCHF2 or OCF3)	B-nO.FN
  CB15	C15
  CBC-nm
  CBC-nmF
  K3.n	M3.n
  PG-n-AN
  PU-n-AN
  PPYRP-nN
  PPYP-nN
  PGP-n-N
  PGIP-n-N
  PVG-N-S
  PVG-nO-S
  PVG-V-S
  PVG-nV-S
  PVG-Vn-S
  PPVU-n-S
  CPVP-n-N
  PTP-n(0)-S
  PTG-n(0)-S
  PTU-n(0)-S
  PTPG-n(0)-N
  GGP-n-CL
  PGIGI-n-CL
  CGU-n-F
  PPU-n-S
  PGU-n-S
  BB3.n
  PPTUI-n-m
  GZU-n-N
  GZU-nO-N
  GZU-nA-N
  UZU-n-N
  UZU-nO-N
  UZU-nA-N
  CUZU-n-N
  BCH-N.Fm
  CFU-n-F
  CBC-nmF
  ECCP-nm
  CCZU-n-F
  T-nFm
  CDU-n-F
  DCU-n-F
  CGG-n-F
  CPZG-n-OT
  CC-nV-Vm
  CCP-Vn-m
  CCG-V-F
  CCP-nV-m
  CC-n-V
  CCQU-n-F
  CC-n-V1
  CCQG-n-F
  CQCU-n-F
  Dec-U-n-F
  CWCU-n-F
  CWCG-n-F
  CCOC-n-m
  CPTU-n-F
  GPTU-n-F
  PQU-n-F
  PUQU-n-F
  PUQU-n-S
  CGU-n-F
  PUQU-n-OT
  PUQU-n-T
  PUZU-n-F
  PGU-n-F
  AUZU-n-F
  AUZU-n-N
  CGZP-n-OT
  CCGU-n-F
  CCQG-n-F
  CUQU-n-F
  CCCQU-n-F
  AGUQU-n-F
  AUUQU-n-F
  AUUQU-n-N
  CUUQU-n-F
  CUUQU-n-OT
  GZU-nA-N
  UZU-nA-N
  AUUQU-n-OT
  AUUQU-n-T
  AUUQP-n-T
  AUUQGU-n-F
  AUUQPU-n-F
  CUZP-nN.F.F
  GZU-nO-N

• Particular preference is given to liquid-crystalline mixtures which, besides the compounds of the formula I, comprise at least one, two, three or four compounds from Table B. Table C:

  Table C shows possible dopants according to component D which are generally added to the mixtures alone or in combination two, three or more) according to the invention.

  C 15

  CB 15

  CM 21

  R/S-811

  CM 44

  CM 45

  CM 47

  R/S-1011

  R/S-3011

  CN

  R/S-2011

  R/S-4011

  R/S-5011

• The liquid crystal media according to the instant invention do contain preferably
• four or more compounds selected from the group of compounds of tables A and B and/or
• five or more compounds selected from the group of compounds of table B and/or
• two or more compounds selected from the group of compounds of table A.
Examples
• The examples given in the following are illustrating the present invention, without limiting it in any way.
• However, the physical data especially of the compounds illustrate to the expert, which properties can be achieved in which ranges. Especially the combination of the various properties, which can be preferably achieved, is thus well defined.
Example 1: Preparation of Bis-2,4,6-Tripropoxy(4',4"biphenol)benzoate:
• 

  4,4'-Biphenol (1.6 g, 8.3 mmol), 2,4,6-tripropoxybenzoic acid (5.0 g, 16.9 mmol) and trifluoroacetic anhydride (4.0 g, 19.0 mmol) in dichloromethane (30 ml) are stirred at room temperature under nitrogen over night. The resultant red solution is neutralized with aqueous sodium carbonate, washed with water and evaporated to dryness. Purification is achieved by preparative HPLC using acetonitrile/ water as eluant to give a white solid. The structure is confirmed by ¹H NMR.The product has a phase sequence of: K 176 I.
Example 2: Preparation of 2,4,6,2",4",6"-Hexapropoxy-[1,1';4',1"]terphenyl:
• 

  1,4- Diiodobenzene (2.60 g, 7.8 mmol), 2,4,6-tripropoxybenzene boronic acid (4.70 g, 15.87 mmol), potassium fluoride (2.0 g, 34.42 mmol), Dioxane (40 ml), potassium phosphate (2.0 g, 9.42 mmol), tetrakis(triphenylphosphine)palladium(0) (166 mg, 0.14 mmol), 2-dicyclohexylphosphino-2-(n.n-dimethylamino)biphenyl(56.6 mg, 0.14 mmol) and tris-dibenzlideneacetone dipalladium(0) (131.9 mg, 0.14 mmol) are stirred under an atmosphere of nitrogen at 75°C for 54 hours. The mixture then is cooled, poured into petrol and passed through a short silica column. Purification is achieved by flash column chromatography to give a white solid. The structure is confirmed by ¹H NMR spectroscopy. The product has a phase sequence of:K 163.4 I
Example 3: Preparation of Bis-2,4,6-tripropoxy(2-methylbenzene(2,2)diol)benzoate
• 

  Methylhydroquinone (0.8 g, 6.7 mmol), 2, 4, 6-tripropoxybenzoic acid (4.0 g, 13.5 mmol) and trifluoroacetic anhydride (3.4 g, 16.1 mmol) in dichloromethane (30 ml) are stirred at room temperature under nitrogen over night. The red solution is neutralized with aqueous sodium carbonate, washed with water and evaporated to dryness. Purification is achieved by flash column chromatography using petrol/dichloromethane (2/1) as eluant to give a white solid. The structure is confirmed by ¹H NMR spectroscopy. The product has a phase sequence of: K 173.6 I.
Example 4: Preparation of Bis-3,4,5-Triethoxy(4',4"biphenol)benzoate:
• 

  4,4'-Biphenol (5.2 g, 27.9 mmol), 3,4,5-triethoxyoxybenzoic acid (7.1 g, 27.9 mmol) and trifluoroacetic anhydride (6.3 g, 30.0 mmol) in dichloromethane (30 ml) are stirred at room temperature under nitrogen over night. The mixture is neutralized with aqueous sodium carbonate, washed with water and evaporated to dryness. Purification is achieved by flash column chromatography using dichloromethane as eluant. The first set of fractions gives upon evaporation the desired diester product as an off-white solid. This crude product is further purified by washing with methanol to yield the product a white solid . The structure is confirmed by ¹H and ¹³C NMR spectroscopy. The product has a phase sequence of: K 205.6 I.
Example 5: Preparation of Bis-[2,6-Dimethoxy-4-(1-propylbutoxy)-1',5'-dihydroxynaphthalene]-benzoate:
• 

  1,5-Dihydroxynaphthalene (1.0 g, 6.2 mmol), 2,6-dimethoxy-4-(1,1-dipropylmethoxy)benzoic acid (3.75 g, 12.7 mmol) and trifluoroacetic anhydride (3.0 g, 14.3 mmol) in dichloromethane (30 ml) are stirred at room temperature under nitrogen over night. The mixture is neutralized with aqueous sodium carbonate, washed with water and evaporated to dryness. Purification is achieved by flash column chromatography using dichloromethane as eluant. The crude product is further purified by recrystallisation from industrial methylated spirit followed by by recrystallisation from acetone to yield the product. The structure is confirmed by ¹H and ¹³C NMR spectroscopy. The product has a phase sequence of: K 183.1 I.
Examples 6 to 68
• Analogously to example 1 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  6	CH3	CH3
  7	C2H5	CH3
  8	n-C3H7	CH3
  9	n-C4H9	CH3
  10	n-C5H11	CH3
  11	n-C6H13	CH3
  12	n-C7H15	CH3
  13	n-C8H17	CH3
  14	n-C9H19	CH3
  15	n-C10H21	CH3
  16	CH2=CH	CH3
  17	CH2=CH-CH2	CH3
  18	CH3-CH=CH	CH3
  19	CH3	C2H5
  4	C2H5	C2H5	C 205.6°C I
  20	n-C3H7	C2H5
  21	n-C4H9	C2H5
  22	n-C5H11	C2H5
  23	n-C6H13	C2H5
  24	n-C7H15	C2H5
  25	n-C8H17	C2H5
  26	n-C9H19	C2H5
  27	n-C10H21	C2H5
  28	CH2=CH	C2H5
  29	CH2=CH-CH2	C2H5
  30	CH3-CH=CH	C2H5
  31	CH3	n-C3H7
  32	C2H5	n-C3H7
  1	n-C3H7	n-C3H7	C 176°C l
  33	n-C4H9	n-C3H7
  34	n-C5H11	n-C3H7
  35	n-C6H13	n-C3H7
  36	n-C7H15	n-C3H7
  37	n-C8H17	n-C3H7
  38	n-C9H19	n-C3H7
  39	n-C10H21	n-C3H7
  40	CH2=CH	n-C3H7
  41	CH2=CH-CH2	n-C3H7
  42	CH3-CH=CH	n-C3H7
  43	CH3	n-C5H11
  44	C2H5	n-C5H11
  45	n-C3H7	n-C5H11
  46	n-C4H9	n-C5H11
  47	n-C5H11	n-C5H11
  48	n-C6H13	n-C5H11
  49	n-C7H15	n-C5H11
  50	n-C8H17	n-C5H11
  51	n-C9H19	n-C5H11
  52	n-C10H21	n-C5H11
  53	CH2=CH	n-C5H11
  54	CH2=CH-CH2	n-C5H11
  55	CH3-CH=CH	n-C5H11
  56	CH3	n-C7H15
  57	C2H5	n-C7H15
  58	n-C3H7	n-C7H15
  59	n-C4H9	n-C7H15
  60	n-C5H11	n-C7H15
  61	n-C6H13	n-C7H15
  62	n-C7H15	n-C7H15
  63	n-C8H17	n-C7H15
  64	n-C9H19	n-C7H15
  65	n-C10H21	n-C7H15
  66	CH2=CH	n-C7H15
  67	CH2=CH-CH2	n-C7H15
  68	CH3-CH=CH	n-C7H15

Examples 69 to 133
• Analogously to example 1 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  69	CH3	CH3
  70	C2H5	CH3
  71	n-C3H7	CH3
  72	n-C4H9	CH3
  73	n-C5H11	CH3
  74	n-C6H13	CH3
  75	n-C7H15	CH3
  76	n-C8H17	CH3
  77	n-C9H19	CH3
  78	n-C10H21	CH3
  79	CH2=CH	CH3
  80	CH2=CH-CH2	CH3
  81	CH3-CH=CH	CH3
  82	CH3	C2H5
  83	C2H5	C2H5
  84	n-C3H7	C2H5
  85	n-C4H9	C2H5
  86	n-C5H11	C2H5
  87	n-C6H13	C2H5
  88	n-C7H15	C2H5
  89	n-C8H17	C2H5
  90	n-C9H19	C2H5
  91	n-C10H21	C2H5
  92	CH2=CH	C2H5
  93	CH2=CH-CH2	C2H5
  94	CH3-CH=CH	C2H5
  95	CH3	n-C3H7
  96	C2H5	n-C3H7
  97	n-C3H7	n-C3H7
  98	n-C4H9	n-C3H7
  99	n-C5H11	n-C3H7
  100	n-C6H13	n-C3H7
  101	n-C7H15	n-C3H7
  102	n-C8H17	n-C3H7
  103	n-C9H19	n-C3H7
  104	n-C10H21	n-C3H7
  105	CH2=CH	n-C3H7
  106	CH2=CH-CH2	n-C3H7
  107	CH3-CH=CH	n-C3H7
  108	CH3	n-C5H11
  109	C2H5	n-C5H11
  110	n-C3H7	n-C5H11
  111	n-C4H9	n-C5H11
  112	n-C5H11	n-C5H11
  113	n-C6H13	n-C5H11
  114	n-C7H15	n-C5H11
  115	n-C8H17	n-C5H11
  116	n-C9H19	n-C5H11
  117	n-C10H21	n-C5H11
  118	CH2=CH	n-C5H11
  119	CH2=CH-CH2	n-C5H11
  120	CH3-CH=CH	n-C5H11
  121	CH3	n-C7H15
  122	C2H5	n-C7H15
  123	n-C3H7	n-C7H15
  124	n-C4H9	n-C7H15
  125	n-C5H11	n-C7H15
  126	n-C6H13	n-C7H15
  127	n-C7H15	n-C7H15
  128	n-C8H17	n-C7H15
  129	n-C9H19	n-C7H15
  130	n-C10H21	n-C7H15
  131	CH2=CH	n-C7H15
  132	CH2=CH-CH2	n-C7H15
  133	CH3-CH=CH	n-C7H15

Examples 134 to 212
• Analogously to example 3 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  134	CH3	CH3
  135	C2H5	CH3
  136	n-C3H7	CH3
  137	n-C4H9	CH3
  138	n-C5H11	CH3
  139	n-C6H13	CH3
  140	n-C7H15	CH3
  141	n-C8H17	CH3
  142	n-C9H19	CH3
  143	n-C10H21	CH3
  144	CH2=CH	CH3
  145	CH2=CH-CH2	CH3
  146	CH3-CH=CH	CH3
  147	CH3	C2H5
  148	C2H5	C2H5
  149	n-C3H7	C2H5
  150	n-C4H9	C2H5
  151	n-C5H11	C2H5
  152	n-C6H13	C2H5
  153	n-C7H15	C2H5
  154	n-C8H17	C2H5
  155	n-C9H19	C2H5
  156	n-C10H21	C2H5
  157	CH2=CH	C2H5
  158	CH2=CH-CH2	C2H5
  159	CH3-CH=CH	C2H5
  160	CH3	n-C3H7
  161	C2H5	n-C3H7
  3	n-C3H7	n-C3H7	C 173.6°C I
  162	n-C4H9	n-C3H7
  163	n-C5H11	n-C3H7
  164	n-C6H13	n-C3H7
  165	n-C7H15	n-C3H7
  166	n-C8H17	n-C3H7
  167	n-C9H19	n-C3H7
  168	n-C10H21	n-C3H7
  169	CH2=CH	n-C3H7
  170	CH2=CH-CH2	n-C3H7
  186	CH3-CH=CH	n-C3H7
  187	CH3	n-C5H11
  188	C2H5	n-C5H11
  189	n-C3H7	n-C5H11
  190	n-C4H9	n-C5H11
  191	n-C5H11	n-C5H11
  192	n-C6H13	n-C5H11
  193	n-C7H15	n-C5H11
  194	n-C8H17	n-C5H11
  195	n-C9H19	n-C5H11
  196	n-C10H21	n-C5H11
  197	CH2=CH	n-C5H11
  198	CH2=CH-CH2	n-C5H11
  199	CH3-CH=CH	n-C5H11
  200	CH3	n-C7H15
  201	C2H5	n-C7H15
  202	n-C3H7	n-C7H15
  203	n-C4H9	n-C7H15
  204	n-C5H11	n-C7H15
  205	n-C6H13	n-C7H15
  206	n-C7H15	n-C7H15
  207	n-C8H17	n-C7H15
  208	n-C9H19	n-C7H15
  209	n-C10H21	n-C7H15
  210	CH2=CH	n-C7H15
  211	CH2=CH-CH2	n-C7H15
  212	CH3-CH=CH	n-C7H15

Examples 213 to 277
• Analogously to example 3 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  213	CH3	CH3
  214	C2H5	CH3
  215	n-C3H7	CH3
  216	n-C4H9	CH3
  217	n-C5H11	CH3
  218	n-C6H13	CH3
  219	n-C7H15	CH3
  220	n-C8H17	CH3
  221	n-C9H19	CH3
  222	n-C10H21	CH3
  223	CH2=CH	CH3
  224	CH2=CH-CH2	CH3
  225	CH3-CH=CH	CH3
  226	CH3	C2H5
  227	C2H5	C2H5
  228	n-C3H7	C2H5
  229	n-C4H9	C2H5
  230	n-C5H11	C2H5
  231	n-C6H13	C2H5
  232	n-C7H15	C2H5
  233	n-C8H17	C2H5
  234	n-C9H19	C2H5
  235	n-C10H21	C2H5
  236	CH2=CH	C2H5
  237	CH2=CH-CH2	C2H5
  238	CH3-CH=CH	C2H5
  239	CH3	n-C3H7
  240	C2H5	n-C3H7
  241	n-C3H7	n-C3H7
  242	n-C4H9	n-C3H7
  243	n-C5H11	n-C3H7
  244	n-C6H13	n-C3H7
  245	n-C7H15	n-C3H7
  246	n-C8H17	n-C3H7
  247	n-C9H19	n-C3H7
  248	n-C10H21	n-C3H7
  249	CH2=CH	n-C3H7
  250	CH2=CH-CH2	n-C3H7
  251	CH3-CH=CH	n-C3H7
  252	CH3	n-C5H11
  253	C2H5	n-C5H11
  254	n-C3H7	n-C5H11
  255	n-C4H9	n-C5H11
  256	n-C5H11	n-C5H11
  257	n-C6H13	n-C5H11
  258	n-C7H15	n-C5H11
  259	n-C8H17	n-C5H11
  260	n-C9H19	n-C5H11
  261	n-C10H21	n-C5H11
  262	CH2=CH	n-C5H11
  263	CH2=CH-CH2	n-C5H11
  264	CH3-CH=CH	n-C5H11
  265	CH3	n-C7H15
  266	C2H5	n-C7H15
  267	n-C3H7	n-C7H15
  268	n-C4H9	n-C7H15
  269	n-C5H11	n-C7H15
  270	n-C6H13	n-C7H15
  271	n-C7H15	n-C7H15
  272	n-C8H17	n-C7H15
  273	n-C9H19	n-C7H15
  274	n-C10H21	n-C7H15
  275	CH2=CH	n-C7H15
  276	CH2=CH-CH2	n-C7H15
  277	CH3-CH=CH	n-C7H15

Examples 278 to 342
• Analogously to example 1 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  278	CH3	CH3
  279	C2H5	CH3
  280	n-C3H7	CH3
  281	n-C4H9	CH3
  282	n-C5H11	CH3
  283	n-C6H13	CH3
  284	n-C7H15	CH3
  285	n-C8H17	CH3
  286	n-C9H19	CH3
  287	n-C10H21	CH3
  288	CH2=CH	CH3
  289	CH2=CH-CH2	CH3
  290	CH3-CH=CH	CH3
  291	CH3	C2H5
  292	C2H5	C2H5
  293	n-C3H7	C2H5
  294	n-C4H9	C2H5
  295	n-C5H11	C2H5
  296	n-C6H13	C2H5
  297	n-C7H15	C2H5
  298	n-C8H17	C2H5
  299	n-C9H19	C2H5
  300	n-C10H21	C2H5
  301	CH2=CH	C2H5
  302	CH2=CH-CH2	C2H5
  303	CH3-CH=CH	C2H5
  304	CH3	n-C3H7
  305	C2H5	n-C3H7
  306	n-C3H7	n-C3H7
  307	n-C4H9	n-C3H7
  308	n-C5H11	n-C3H7
  309	n-C6H13	n-C3H7
  310	n-C7H15	n-C3H7
  311	n-C8H17	n-C3H7
  312	n-C9H19	n-C3H7
  313	n-C10H21	n-C3H7
  314	CH2=CH	n-C3H7
  315	CH2=CH-CH2	n-C3H7
  316	CH3-CH=CH	n-C3H7
  317	CH3	n-C5H11
  318	C2H5	n-C5H11
  319	n-C3H7	n-C5H11
  320	n-C4H9	n-C5H11
  321	n-C5H11	n-C5H11
  322	n-C6H13	n-C5H11
  323	n-C7H15	n-C5H11
  324	n-C8H17	n-C5H11
  325	n-C9H19	n-C5H11
  326	n-C10H21	n-C5H11
  327	CH2=CH	n-C5H11
  328	CH2=CH-CH2	n-C5H11
  329	CH3-CH=CH	n-C5H11
  330	CH3	n-C7H15
  331	C2H5	n-C7H15
  332	n-C3H7	n-C7H15
  333	n-C4H9	n-C7H15
  334	n-C5H11	n-C7H15
  335	n-C6H13	n-C7H15
  336	n-C7H15	n-C7H15
  337	n-C8H17	n-C7H15
  338	n-C9H19	n-C7H15
  339	n-C10H21	n-C7H15
  340	CH2=CH	n-C7H15
  341	CH2=CH-CH2	n-C7H15
  342	CH3-CH=CH	n-C7H15

Examples 343 to 407
• Analogously to example 1 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  343	CH3	CH3
  344	C2H5	CH3
  345	n-C3H7	CH3
  346	n-C4H9	CH3
  347	n-C5H11	CH3
  348	n-C6H13	CH3
  349	n-C7H15	CH3
  350	n-C8H17	CH3
  351	n-C9H19	CH3
  352	n-C10H21	CH3
  353	CH2=CH	CH3
  354	CH2=CH-CH2	CH3
  355	CH3-CH=CH	CH3
  356	CH3	C2H5
  357	C2H5	C2H5
  358	n-C3H7	C2H5
  359	n-C4H9	C2H5
  360	n-C5H11	C2H5
  361	n-C6H13	C2H5
  362	n-C7H15	C2H5
  363	n-C8H17	C2H5
  364	n-C9H19	C2H5
  365	n-C10H21	C2H5
  366	CH2=CH	C2H5
  367	CH2=CH-CH2	C2H5
  368	CH3-CH=CH	C2H5
  369	CH3	n-C3H7
  370	C2H5	n-C3H7
  371	n-C3H7	n-C3H7
  372	n-C4H9	n-C3H7
  373	n-C5H11	n-C3H7
  374	n-C6H13	n-C3H7
  375	n-C7H15	n-C3H7
  376	n-C8H17	n-C3H7
  377	n-C9H19	n-C3H7
  378	n-C10H21	n-C3H7
  379	CH2=CH	n-C3H7
  380	CH2=CH-CH2	n-C3H7
  381	CH3-CH=CH	n-C3H7
  382	CH3	n-C5H11
  383	C2H5	n-C5H11
  384	n-C3H7	n-C5H11
  385	n-C4H9	n-C5H11
  386	n-C5H11	n-C5H11
  387	n-C6H13	n-C5H11
  388	n-C7H15	n-C5H11
  389	n-C8H17	n-C5H11
  390	n-C9H19	n-C5H11
  391	n-C10H21	n-C5H11
  392	CH2=CH	n-C5H11
  393	CH2=CH-CH2	n-C5H11
  394	CH3-CH=CH	n-C5H11
  395	CH3	n-C7H15
  396	C2H5	n-C7H15
  397	n-C3H7	n-C7H15
  398	n-C4H9	n-C7H15
  399	n-C5H11	n-C7H15
  400	n-C6H13	n-C7H15
  401	n-C7H15	n-C7H15
  402	n-C8H17	n-C7H15
  403	n-C9H19	n-C7H15
  404	n-C10H21	n-C7H15
  405	CH2=CH	n-C7H15
  406	CH2=CH-CH2	n-C7H15
  407	CH3-CH=CH	n-C7H15

Examples 408 to 472
• Analogously to example 5 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  408	CH3	CH3
  409	C2H5	CH3
  410	n-C3H7	CH3
  411	n-C4H9	CH3
  412	n-C5H11	CH3
  413	n-C6H13	CH3
  414	n-C7H15	CH3
  415	n-C8H17	CH3
  416	n-C9H19	CH3
  417	n-C10H21	CH3
  418	CH2=CH	CH3
  419	CH2=CH-CH2	CH3
  420	CH3-CH=CH	CH3
  421	CH3	C2H5
  422	C2H5	C2H5
  423	n-C3H7	C2H5
  424	n-C4H9	C2H5
  425	n-C5H11	C2H5
  426	n-C6H13	C2H5
  427	n-C7H15	C2H5
  428	n-C8H17	C2H5
  429	n-C9H19	C2H5
  430	n-C10H21	C2H5
  431	CH2=CH	C2H5
  432	CH2=CH-CH2	C2H5
  433	CH3-CH=CH	C2H5
  434	CH3	n-C3H7
  435	C2H5	n-C3H7
  436	n-C3H7	n-C3H7
  437	n-C4H9	n-C3H7
  438	n-C5H11	n-C3H7
  439	n-C6H13	n-C3H7
  440	n-C7H15	n-C3H7
  441	n-C8H17	n-C3H7
  442	n-C9H19	n-C3H7
  443	n-C10H21	n-C3H7
  444	CH2=CH	n-C3H7
  445	CH2=CH-CH2	n-C3H7
  446	CH3-CH=CH	n-C3H7
  447	CH3	n-C5H11
  448	C2H5	n-C5H11
  449	n-C3H7	n-C5H11
  450	n-C4H9	n-C5H11
  451	n-C5H11	n-C5H11
  452	n-C6H13	n-C5H11
  453	n-C7H15	n-C5H11
  454	n-C8H17	n-C5H11
  455	n-C9H19	n-C5H11
  456	n-C10H21	n-C5H11
  457	CH2=CH	n-C5H11
  458	CH2=CH-CH2	n-C5H11
  459	CH3-CH=CH	n-C5H11
  460	CH3	n-C7H15
  461	C2H5	n-C7H15
  462	n-C3H7	n-C7H15
  463	n-C4H9	n-C7H15
  464	n-C5H11	n-C7H15
  465	n-C6H13	n-C7H15
  466	n-C7H15	n-C7H15
  467	n-C8H17	n-C7H15
  468	n-C9H19	n-C7H15
  469	n-C10H21	n-C7H15
  470	CH2=CH	n-C7H15
  471	CH2=CH-CH2	n-C7H15
  472	CH3-CH=CH	n-C7H15

Examples 473 to 537
• Analogously to example 5 the following compounds are prepared:

  

  No.	R'	R"	Phases (T/°C)
  473	CH3	CH3
  474	C2H5	CH3
  475	n-C3H7	CH3
  476	n-C4H9	CH3
  477	n-C5H11	CH3
  478	n-C6H13	CH3
  479	n-C7H15	CH3
  480	n-C8H17	CH3
  481	n-C9H19	CH3
  482	n-C10H21	CH3
  483	CH2=CH	CH3
  484	CH2=CH-CH2	CH3
  485	CH3-CH=CH	CH3
  486	CH3	C2H5
  487	C2H5	C2H5
  488	n-C3H7	C2H5
  489	n-C4H9	C2H5
  490	n-C5H11	C2H5
  491	n-C6H13	C2H5
  492	n-C7H15	C2H5
  493	n-C8H17	C2H5
  494	n-C9H19	C2H5
  495	n-C10H21	C2H5
  496	CH2=CH	C2H5
  497	CH2=CH-CH2	C2H5
  498	CH3-CH=CH	C2H5
  499	CH3	n-C3H7
  500	C2H5	n-C3H7
  501	n-C3H7	n-C3H7
  502	n-C4H9	n-C3H7
  503	n-C5H11	n-C3H7
  504	n-C6H13	n-C3H7
  505	n-C7H15	n-C3H7
  506	n-C8H17	n-C3H7
  507	n-C9H19	n-C3H7
  508	n-C10H21	n-C3H7
  509	CH2=CH	n-C3H7
  510	CH2=CH-CH2	n-C3H7
  511	CH3-CH=CH	n-C3H7
  512	CH3	n-C5H11
  513	C2H5	n-C5H11
  514	n-C3H7	n-C5H11
  515	n-C4H9	n-C5H11
  516	n-C5H11	n-C5H11
  517	n-C6H13	n-C5H11
  518	n-C7H15	n-C5H11
  519	n-C8H17	n-C5H11
  520	n-C9H19	n-C5H11
  521	n-C10H21	n-C5H11
  522	CH2=CH	n-C5H11
  523	CH2=CH-CH2	n-C5H11
  524	CH3-CH=CH	n-C5H11
  525	CH3	n-C7H15
  526	C2H5	n-C7H15
  527	n-C3H7	n-C7H15
  528	n-C4H9	n-C7H15
  529	n-C5H11	n-C7H15
  530	n-C6H13	n-C7H15
  531	n-C7H15	n-C7H15
  532	n-C8H17	n-C7H15
  533	n-C9H19	n-C7H15
  534	n-C10H21	n-C7H15
  535	CH2=CH	n-C7H15
  536	CH2=CH-CH2	n-C7H15
  537	CH3-CH=CH	n-C7H15

Comparative Use-example
• 5% of the chiral agent R-5011 are solved in the achiral liquid crystal mixture H-0 with the composition and properties given in table 1 below. Table 1: Composition and Properties of Host Mixture H-0

  Compound Abbreviation	Concentration /mass-%	Physical Properties
  GZU-3A-N	15.0	T(N, I) = 56.5 °C
  GZU-4A-N	15.0
  GZU-40-N	15.0	Δn (20°C, 589 nm) = 0.164
  UZU-3A-N	8.0
  CUZU-2-N	9.0
  CUZU-3-N	9.0
  CUZU-4-N	9.0
  HP-3N.F	6.0
  HP-4N.F	6.0
  HP-5N.F	8.0
  Σ	100.0

• The resulting mixture CM-0 is filled into an electro optical test cell with interdigital electrodes on one substrate side. The electrode width is 10 µm, the distance between adjacent electrodes is 10 µm and the cell gap is also 10 µm. This test cell is evaluated electro-optically between crossed polarisers.
• At low temperatures, the filled cell showed the typical texture of a chiral nematic mixture, with an optical transmission between crossed polarisers without applied voltage. On heating, at a temperature of 36°C the mixture was optically isotropic, being dark between the crossed polarisers.
• This indicated the transition from the chiral nematic phase to the blue phase at 36°C. This temperature is called T₁ or T_trans.
• Up to a temperature of 43°C the cell shows a clear electro optical effect under applied voltage, for example at 38°C, applying a voltage of 46 V leads to a maximum of the optical transition. This temperature is called T₂ and threspective voltage is called V_max or V₁₀₀. At a temperature of 43°C the voltage needed for a visible electro-optical effect starts to increase strongly, indicating the transition from the blue phase to the isotropic phase at this temperature.
• The temperature range (ΔT(BP)), where the mixture can be used electro-optically in the blue phase is identified as ranging from about 36°C to about 43°C, i.e. as being 7° wide (= T₂ - T₁ = 43°C - 36°C). The results are listed in table 2 below. Further the response times for switching on (τ_on) and for switching off (τ_off) are been determined. The response times decrease with increasing temperature above T₁ and the temperature at which both response times have fallen below 5 ms each is called T₃. This is the case in this comparative use example at a temperature of about 39.3°C or slightly above. Thus, the range of usable flat behaviour i.e. the usable flat range (ΔT(FR)), which is defined as ΔT(FR) = T₂ - T₃, in case T₂ ≥ T₃ and ΔT(FR) = 0, in case T₂ < T₃, is (43.0°C-39.3°C) = 3,7° in this comparative use example.
Use-example 1
• In this use-example 10 % of the compound of example 1 are solved together with 5% of the chiral agent R-5011 in the achiral liquid crystal mixture H-0 used in the comparative use-example described above. The resultant mixtures H-1 hs the composition and properties shown in table 2. Table 2: Results

  Use-Ex. #	C.E.	1	2	3	4	5
  Mixture #	CM-0	H-1	H-2	H-3	H-4	H-5
  Cpd. of Ex. #	None	1	2	3	4	5
  c(Cpd.)/%	0	10	5		10	5
  c(R-5011)/%	0	5

  Characteristic Temparatures
  T2/°C	43.0	22.0	n.d.	26.1	n.d.	11.7
  T3/°C	39.3	19.0	n.d.	20.1	n.d.	11.7
  T1/°C	36.0	20.0	n.d.	18.6	n.d.	0.8
  ΔT(BP)/°	7.0	9.0	n.d.	9.5	n.d.	10.9
  ΔT(FR)/°	3.7	3.0	n.d.	6.0	n.d.	0.0

  Characteristic Voltages
  Top./°C	38.0	22.0	n.d.	26.1	n.d.	9.7
  Vmax/V	46.0	40.0	n.d.	38.8	n.d.	43.5
  dVmax/dT/V/°	n.d.	4.5	n.d.	1.2	n.d.	0.0
  dVmax/dT/V0/°	n.d.	0.11	n.d.	0.03	n.d.	0.00

  Remarks: n.d.: not determined.

• The resulting mixtures H-1 is filled into a respective electro optical test cells like those used in the comparative use-example and investigated as described there.
• At low temperatures, the cell filled with the mixture H―1 shows the typical texture of a chiral nematic mixture, with an optical transmission between crossed polarisers without applied voltage. On heating, at a temperature of 20.0°C the mixture becomes optically isotropic, being dark between the crossed polarisers. This indicates the transition from the chiral nematic phase to the blue phase at 20.0°C. Up to a temperature of 29.0°C, the cell shows a clear electro optical effect under applied voltage. For example at 22.0°C, applying 40.0 volts leads to a maximum of the optical transition. At a temperature of 29.0°C the voltage needed for a visible electro-optical effect increases strongly, indicating the transition from the blue phase to the isotropic phase at 29.0°C.
• The range, where the mixture can be used electro-optically in the blue phase is thus identified as 29.0C - 20.0°C = 9.0°.
• This is significantly larger than the range of 7°, being found in the mixture CM-0 of the comparative use example 1, which is containg 5% R-5011, only. The results are listed in table 2.
Use-examples 2 to 5
• In these use-examples alternatively one each of the the compounds of examples 2 to 5 are solved in the respective concentration(s) given in table 2 (either 5% or 10%) each together with 5% of the chiral agent R-5011 in the achiral liquid crystal mixture H-0 used in the comparative use-example described above. The resultant mixtures H-2 to H-5 have the compositions and properties shown in table 2.
• The mixtures H-2 to H-5 are investigated in the same way as the mixture H-1. The results are also listed in table 2. All use-examples investigated show a larger temperature range compared to the comparative use-example and at the same time the chatracteristc voltage even is reduced significantly.

Claims (12)

1. Mesogenic medium comprising one or more compounds of formula I

   

   wherein

   R¹¹ to R¹⁶ are, independently of each other, alkyl, which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or poly-substituted by F, Cl, or CN, and in which one or more non-adjacent CH₂ groups are optionally replaced, in each case independently from one another, by -O-, -CH=CH- or -C≡C- in such a manner that O atoms are not linked directly to one another,

   MG is a bivalent mesogenic group and

   

   or

   

   or

   

   and

   
2. Medium according to claim 1, characterized in that it has a blue phase.
3. Medium according to at least one of claims 1 and 2, characterized in that it comprises one or more compounds of formula I
   wherein

   R¹¹ to R¹⁶ are, independently of each other, alkyl, alkoxy, alkenyl or alkynyl.
4. Medium according to one or more of claims 1 to 3, characterized in that it comprises one or more compounds of formula I wherein

   MG is a bivalent mesogenic group of formula

   

   wherein

   

   is and, in case it is occurring more than once, also these are in each occurrence, independently of each other, an aromatic and/or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and/or S, and are optionally monosubstituted or polysubstituted by R,

   R has the meaning given for R¹¹ or is

   

   and preferably is
   halogen, CN, or alkyl, and most preferably F, CN or alkyl with 1 to 12 C-atoms,

   Z¹¹ and Z¹² are, independently of each other, and in case Z¹¹ is occurring more than once, also these are in each occurrence independently of each other, -O-, -S-, -CO-O-, -O-CO-, -O -CO-O-, -S-CO-, -CO-S-, -CO-NR⁰¹-, -NR⁰¹-CO-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CH₂CH₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰¹-, -CR⁰¹=CH-, -CY⁰¹=CY⁰²-, -C≡C-, -(CH₂)₄-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond,

   Y⁰¹ and Y⁰² are, independently of each other, F, Cl or CN, andalternatively one of them may be H,

   R⁰¹ and R⁰² are, independently of each other, H or alkyl with 1 to 12C-atoms,

   m is 1, 2, 3, 4, 5 or 6, and

   n is 0, 1 or 2.
5. Medium according to one or more of claims 1 to 4, characterized in that it comprises one or more compounds of formula I according to claim 3 wherein

   
6. Compound of formula I

   

   wherein the parameters have the respective meanings given in claim 1.
7. Compound according to claim 6, characterized in that the parameter MG has the meaning given in claim 4.
8. Compound according to at one or more of claims 6 and 7,
   characterized in that

   
9. Light modulation element, characterized in that it comprises a medium according to one or more of claims 1 to 5.
10. Use of a compound according to one or more of claims 6 to 8 in a mesogenic medium.
11. Use of a medium according to at one or more of claims 1 to 5 in a light modulation element.
12. Electro-optical display, characterized in that it comprises a medium according to one or more of claims 1 to 6.